One of the conventionally known methods for driving display devices, such as liquid crystal display devices, is a method called SSD (source-shared driving; referred to below as an “SSD method”). In a liquid crystal display device employing the SSD method, a plurality of output terminals of a source driver (video signal line driver circuit) for driving a plurality of source lines (video signal lines) on a liquid crystal panel are connected to a selection circuit consisting of a plurality of switching elements such as thin-film transistors. Each output terminal of the source driver is connected to a predetermined number of the thin-film transistors. The thin-film transistors in the selection circuit are connected to a plurality of source lines. Specifically, in this liquid crystal display device, groups of the predetermined number of source lines are connected to the output terminals of their common source driver via the predetermined number of thin-film transistors. Moreover, a video signal that is common among the groups is provided to the source driver, and the selection circuit applies the video signal to the source lines in a time-division manner. By employing the SSD method as above, it is rendered possible to reduce the number of output terminals of the source driver.
Patent Document 1 discloses a liquid crystal display device employing the SSD method and having the selection circuit integrally formed with a liquid crystal panel. In the following, such a liquid crystal display device with the selection circuit integrally formed with a liquid crystal panel (display portion) will be referred to as a “liquid crystal display device with a monolithic selection circuit”. This liquid crystal display device with a monolithic selection circuit allows a frame area reduction and a cost reduction. For example, thin-film transistors using amorphous silicon (a-Si) for their semiconductor layers (referred to below as “a-Si TFTs ”) are used as driver elements of the liquid crystal display device with a monolithic selection circuit, as disclosed in Patent Document 1.
Incidentally, Patent Document 2 discloses a display device drive method in which a scanning period T1 for scanning gate lines (scanning signal lines) is followed by an idle period T2 in which no gate lines are scanned. During the idle period T2, clock signals, etc., are not provided to a gate driver (scanning signal line driver circuit), so that image rewriting is not performed. Accordingly, even in the case where the gate lines are scanned at 60 Hz during the scanning period T1, when the idle period T2, which has, for example, the same length as the scanning period T1, is provided, the overall frequency for driving the gate lines is about 30 Hz. Thus, a reduction in power consumption can be achieved.